Pyridoxine deficiency
Encyclopedia
Pyridoxine deficiency is a paediatric disease due to a lack of pyridoxine
(or vitamin B6). It usually becomes noticeable within the first 12 months of life in infants with a lack of pyridoxine, a coenzyme responsible for numerous essential metabolic
reactions in humans. It is rarely observed, even in developing countries.
, cheilitis
(inflammation of the lips), conjunctivitis
and neurologic symptoms. In patients receiving isoniazid, pyridoxine deficiency can lead to a sideroblastic anemia
because pyridoxine is a required cofactor in heme synthesis.
causes seizures at birth or shortly afterwards. It has been speculated that the cause of seizures in pyridoxine deficiency lies with abnormalities in the normal ratio of glutamic acid to GABA. Association is noted with ALDH7A1
gene. Irritability and other neurologic symptoms, such as confusion, are common place.. Anemia
has also been documented as a symptom.
medication isoniazid
, and for this reason, it is usually replaced with vitamin B6 whilst using this drug.
of glutamic acid
to gamma-aminobutyric acid
(GABA, a neurotransmitter
) and transamination
of glutamic acid to alpha-ketoglutaric acid are both impaired in animals when suffering from pyridoxine deficiency. Neurologic symptoms are most likely due to diminished affinity of pyridoxine for the apoenzyme, which can only be overcome by increasing tissue concentrations of the enzyme.
, and occurred in a small percentage of infants who were fed a formula lacking in pyridoxine. A positive diagnosis test for pyridoxine deficiency can be ascertained by measuring erythrocyte levels of aspartate aminotransferase and transketolase
in serum
.
or hydrazide
s, such as isoniazid
, are rarely used due to their ability to provoke deficiency symptoms.
Pyridoxine
Pyridoxine is one of the compounds that can be called vitamin B6, along with pyridoxal and pyridoxamine. It differs from pyridoxamine by the substituent at the '4' position. It is often used as 'pyridoxine hydrochloride'.-Chemistry:...
(or vitamin B6). It usually becomes noticeable within the first 12 months of life in infants with a lack of pyridoxine, a coenzyme responsible for numerous essential metabolic
Metabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...
reactions in humans. It is rarely observed, even in developing countries.
Symptoms
The disease presents with several key symptoms including seizures, irritabilityIrritability
Irritability is an excessive response to stimuli. The term is used for both the physiological reaction to stimuli and for the pathological, abnormal or excessive sensitivity to stimuli; It is usually used to refer to anger or frustration....
, cheilitis
Cheilitis
Cheilitis is a medical condition involving inflammation of the lip.It is associated with many conditions, including megaloblastic anemia from vitamin B12 deficiency, iron deficiency anemia and oral candidiasis. It can also be a symptom of allergies, such as allergy to Balsam of Peru...
(inflammation of the lips), conjunctivitis
Conjunctivitis
Conjunctivitis refers to inflammation of the conjunctiva...
and neurologic symptoms. In patients receiving isoniazid, pyridoxine deficiency can lead to a sideroblastic anemia
Sideroblastic anemia
Sideroblastic anemia or sideroachrestic anemia is a disease in which the bone marrow produces ringed sideroblasts rather than healthy red blood cells . It may be caused either by a genetic disorder or indirectly as part of myelodysplastic syndrome, which can evolve into hematological malignancies...
because pyridoxine is a required cofactor in heme synthesis.
Rare forms
Familial pyridoxine-dependent epilepsyPyridoxine-dependent epilepsy
Pyridoxine-dependent epilepsy or pyridoxine-dependent seizure is an extremely rare disorder characterised by intractable seizures in newborn children that require lifelong B6 supplementation to treat. The disorder was first recognized in the 1950, with the first description provided by Hunt et...
causes seizures at birth or shortly afterwards. It has been speculated that the cause of seizures in pyridoxine deficiency lies with abnormalities in the normal ratio of glutamic acid to GABA. Association is noted with ALDH7A1
ALDH7A1
Aldehyde dehydrogenase 7 family, member A1 also known as ALDH7A1 or antiquitin is an enzyme that in humans is encoded by the ALDH7A1 gene.-Function:...
gene. Irritability and other neurologic symptoms, such as confusion, are common place.. Anemia
Anemia
Anemia is a decrease in number of red blood cells or less than the normal quantity of hemoglobin in the blood. However, it can include decreased oxygen-binding ability of each hemoglobin molecule due to deformity or lack in numerical development as in some other types of hemoglobin...
has also been documented as a symptom.
Causes
The main cause of pyridoxine deficiency is a lack of pyridoxine in the diet. Another cause of vitamin B6 deficiency is the use of the tuberculostaticTuberculosis
Tuberculosis, MTB, or TB is a common, and in many cases lethal, infectious disease caused by various strains of mycobacteria, usually Mycobacterium tuberculosis. Tuberculosis usually attacks the lungs but can also affect other parts of the body...
medication isoniazid
Isoniazid
Isoniazid , also known as isonicotinylhydrazine , is an organic compound that is the first-line antituberculosis medication in prevention and treatment. It was first discovered in 1912, and later in 1951 it was found to be effective against tuberculosis by inhibiting its mycolic acid...
, and for this reason, it is usually replaced with vitamin B6 whilst using this drug.
Pathophysiology
DecarboxylationDecarboxylation
Decarboxylation is a chemical reaction that releases carbon dioxide . Usually, decarboxylation refers to a reaction of carboxylic acids, removing a carbon atom from a carbon chain. The reverse process, which is the first chemical step in photosynthesis, is called carbonation, the addition of CO2 to...
of glutamic acid
Glutamic acid
Glutamic acid is one of the 20 proteinogenic amino acids, and its codons are GAA and GAG. It is a non-essential amino acid. The carboxylate anions and salts of glutamic acid are known as glutamates...
to gamma-aminobutyric acid
Gamma-aminobutyric acid
γ-Aminobutyric acid is the chief inhibitory neurotransmitter in the mammalian central nervous system. It plays a role in regulating neuronal excitability throughout the nervous system...
(GABA, a neurotransmitter
Neurotransmitter
Neurotransmitters are endogenous chemicals that transmit signals from a neuron to a target cell across a synapse. Neurotransmitters are packaged into synaptic vesicles clustered beneath the membrane on the presynaptic side of a synapse, and are released into the synaptic cleft, where they bind to...
) and transamination
Transamination
There are two chemical reactions known as transamination . The first is the reaction between an amino acid and an alpha-keto acid...
of glutamic acid to alpha-ketoglutaric acid are both impaired in animals when suffering from pyridoxine deficiency. Neurologic symptoms are most likely due to diminished affinity of pyridoxine for the apoenzyme, which can only be overcome by increasing tissue concentrations of the enzyme.
Diagnosis
Pyridoxine deficiency is a very rare condition, even in developing countries. A handful of cases were seen in between 1952 and 1953, particularly in the United StatesUnited States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, and occurred in a small percentage of infants who were fed a formula lacking in pyridoxine. A positive diagnosis test for pyridoxine deficiency can be ascertained by measuring erythrocyte levels of aspartate aminotransferase and transketolase
Transketolase
Transketolase, an enzyme of both the pentose phosphate pathway in animals and the Calvin cycle of photosynthesis, catalyzes two important reactions, which operate in opposite directions in these two pathways...
in serum
Blood plasma
Blood plasma is the straw-colored liquid component of blood in which the blood cells in whole blood are normally suspended. It makes up about 55% of the total blood volume. It is the intravascular fluid part of extracellular fluid...
.
Treatment
Treatment of pyridoxine deficiency lies with replacing the missing vitamin. PenicillaminePenicillamine
Penicillamine is a pharmaceutical of the chelator class. It is sold under the trade names of Cuprimine and Depen. The pharmaceutical form is D-penicillamine, as L-penicillamine is toxic...
or hydrazide
Hydrazide
Hydrazides in organic chemistry are a class of organic compounds sharing a common functional group characterized by a nitrogen to nitrogen covalent bond with 4 substituents with at least one of them being an acyl group. The general structure for an hydrazide is R2-N-N-R3R4. A related class of...
s, such as isoniazid
Isoniazid
Isoniazid , also known as isonicotinylhydrazine , is an organic compound that is the first-line antituberculosis medication in prevention and treatment. It was first discovered in 1912, and later in 1951 it was found to be effective against tuberculosis by inhibiting its mycolic acid...
, are rarely used due to their ability to provoke deficiency symptoms.